158 research outputs found
Beyond East & West: Hellenistic commagene between particularism and universalism
NWOClassical & Mediterranean Archaeolog
Common dwelling place of all the gods: commagene in its local, regional and global Hellenistic context
NWOClassical & Mediterranean Archaeolog
The long-time dynamics of two hydrodynamically-coupled swimming cells
Swimming micro-organisms such as bacteria or spermatozoa are typically found
in dense suspensions, and exhibit collective modes of locomotion qualitatively
different from that displayed by isolated cells. In the dilute limit where
fluid-mediated interactions can be treated rigorously, the long-time
hydrodynamics of a collection of cells result from interactions with many other
cells, and as such typically eludes an analytical approach. Here we consider
the only case where such problem can be treated rigorously analytically, namely
when the cells have spatially confined trajectories, such as the spermatozoa of
some marine invertebrates. We consider two spherical cells swimming, when
isolated, with arbitrary circular trajectories, and derive the long-time
kinematics of their relative locomotion. We show that in the dilute limit where
the cells are much further away than their size, and the size of their circular
motion, a separation of time scale occurs between a fast (intrinsic) swimming
time, and a slow time where hydrodynamic interactions lead to change in the
relative position and orientation of the swimmers. We perform a multiple-scale
analysis and derive the effective dynamical system - of dimension two -
describing the long-time behavior of the pair of cells. We show that the system
displays one type of equilibrium, and two types of rotational equilibrium, all
of which are found to be unstable. A detailed mathematical analysis of the
dynamical systems further allows us to show that only two cell-cell behaviors
are possible in the limit of , either the cells are attracted to
each other (possibly monotonically), or they are repelled (possibly
monotonically as well), which we confirm with numerical computations
Methane sources in gas hydrate-bearing cold-seeps : evidence from radiocarbon and stable isotopes
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 115 (2009): 102-109, doi:10.1016/j.marchem.2009.07.001.Fossil methane from the large and dynamic marine gas hydrate reservoir has the potential to influence oceanic and atmospheric carbon pools. However, natural radiocarbon (14C) measurements of gas hydrate methane have been extremely limited, and their use as a source and process indicator has not yet been systematically established. In this study, gas hydrate-bound and dissolved methane recovered from six geologically and geographically distinct high-gas-flux cold seeps was found to be 98 to 100% fossil based on its 14C content. Given this prevalence of fossil methane and the small contribution of gas hydrate (â€1%) to the present-day atmospheric methane flux, non-fossil contributions of gas hydrate methane to the atmosphere are not likely to be quantitatively significant. This conclusion is consistent with contemporary atmospheric methane budget calculations.
In combination with ÎŽ13C- and ÎŽD-methane measurements, we also determine the extent to which the low, but detectable, amounts of 14C (~ 1-2 percent modern carbon, pMC) in methane from two cold seeps might reflect in situ production from near-seafloor sediment organic carbon (SOC). A 14C mass balance approach using fossil methane and 14C-enriched SOC suggests that as much as 8 to 29% of hydrate-associated methane carbon may originate from SOC contained within the upper 6 meters of sediment. These findings validate the assumption of a predominantly fossil carbon source for marine gas hydrate, but also indicate that structural gas hydrate from at least certain cold seeps contains a component of methane produced during decomposition of non-fossil organic matter in near-surface sediment.This work was supported by the Office of Naval Research and Naval Research
Laboratory (NRL). Partial support was also provided by
the USGS Mendenhall Postdoctoral Research Fellowship Program to JWP, and NSF
Chemical Oceanography (OCE-0327423) and Integrated Carbon Cycle Research (EAR-
0403949) program support to JEB
All-particle cosmic ray energy spectrum measured with 26 IceTop stations
We report on a measurement of the cosmic ray energy spectrum with the IceTop
air shower array, the surface component of the IceCube Neutrino Observatory at
the South Pole. The data used in this analysis were taken between June and
October, 2007, with 26 surface stations operational at that time, corresponding
to about one third of the final array. The fiducial area used in this analysis
was 0.122 km^2. The analysis investigated the energy spectrum from 1 to 100 PeV
measured for three different zenith angle ranges between 0{\deg} and 46{\deg}.
Because of the isotropy of cosmic rays in this energy range the spectra from
all zenith angle intervals have to agree. The cosmic-ray energy spectrum was
determined under different assumptions on the primary mass composition. Good
agreement of spectra in the three zenith angle ranges was found for the
assumption of pure proton and a simple two-component model. For zenith angles
{\theta} < 30{\deg}, where the mass dependence is smallest, the knee in the
cosmic ray energy spectrum was observed between 3.5 and 4.32 PeV, depending on
composition assumption. Spectral indices above the knee range from -3.08 to
-3.11 depending on primary mass composition assumption. Moreover, an indication
of a flattening of the spectrum above 22 PeV were observed.Comment: 38 pages, 17 figure
An improved method for measuring muon energy using the truncated mean of dE/dx
The measurement of muon energy is critical for many analyses in large
Cherenkov detectors, particularly those that involve separating
extraterrestrial neutrinos from the atmospheric neutrino background. Muon
energy has traditionally been determined by measuring the specific energy loss
(dE/dx) along the muon's path and relating the dE/dx to the muon energy.
Because high-energy muons (E_mu > 1 TeV) lose energy randomly, the spread in
dE/dx values is quite large, leading to a typical energy resolution of 0.29 in
log10(E_mu) for a muon observed over a 1 km path length in the IceCube
detector. In this paper, we present an improved method that uses a truncated
mean and other techniques to determine the muon energy. The muon track is
divided into separate segments with individual dE/dx values. The elimination of
segments with the highest dE/dx results in an overall dE/dx that is more
closely correlated to the muon energy. This method results in an energy
resolution of 0.22 in log10(E_mu), which gives a 26% improvement. This
technique is applicable to any large water or ice detector and potentially to
large scintillator or liquid argon detectors.Comment: 12 pages, 16 figure
High-dose carfilzomib achieves superior anti-tumor activity over lowdose and recaptures response in relapsed/refractory multiple myeloma resistant to low-dose carfilzomib by co-inhibiting the ÎČ2 and ÎČ1 subunits of the proteasome complex
The optimal carfilzomib dosing is a matter of debate. We analyzed the inhibition profiles of proteolytic proteasome subunits ÎČ5, ÎČ2 and ÎČ1 after low-dose (20/27 mg/m2) versus high-dose (â„36 mg/m2) carfilzomib in 103 pairs of peripheral blood mononuclear cells from patients with relapsed/refractory (RR) multiple myeloma (MM). ÎČ5 activity was inhibited (median inhibition >50%) in vivo by 20 mg/m2, whereas ÎČ2 and ÎČ1 were co-inhibited only by 36 and 56 mg/m2, respectively. Co-inhibition of ÎČ2 (P=0.0001) and ÎČ1 activity (P=0.0005) differed significantly between high-dose and low-dose carfilzomib. Subsequently, high-dose carfilzomib showed significantly more effective proteasome inhibition than low-dose drug in vivo (P=0.0003). We investigated the clinical data of 114 patients treated with carfilzomib combinations. High-dose carfilzomib demonstrated a higher overall response rate (P=0.03) and longer progression-free survival (PFS) (P=0.007) than low-dose carfilzomib. Therefore, we escalated the carfilzomib dose to â„ 36 mg/m2 in 16 patients who progressed during low-dose carfilzomib-containing therapies. High-dose carfilzomib recaptured response (â„ partial remission) in 9 (56%) patients with a median PFS of 4.4 months. Altogether, we provide the first in vivo evidence in RRMM patients that the molecular activity of high-dose carfilzomib differs from that of low-dose carfilzomib by co-inhibition of ÎČ2 and ÎČ1 proteasome subunits and, consequently, high-dose carfilzomib achieves a superior anti-MM effect than low-dose and recaptures response in RRMM being resistant to low-dose carfilzomib. The optimal carfilzomib dose should be â„ 36 mg/m2 to reach a sufficient anti-tumor activity, while the balance between efficacy and tolerability should be considered in each patient.Bio-organic Synthesi
Determinants of cognitive performance and decline in 20 diverse ethno-regional groups: A COSMIC collaboration cohort study
Background: With no effective treatments for cognitive decline or dementia, improving the evidence base for modifiable risk factors is a research priority. This study investigated associations between risk factors and late-life cognitive decline on a global scale, including comparisons between ethno-regional groups. Methods and findings: We harmonized longitudinal data from 20 population-based cohorts from 15 countries over 5 continents, including 48,522 individuals (58.4% women) aged 54â105 (mean = 72.7) years and without dementia at baseline. Studies had 2â15 years of follow-up. The risk factors investigated were age, sex, education, alcohol consumption, anxiety, apolipoprotein E Δ4 allele (APOE*4) status, atrial fibrillation, blood pressure and pulse pressure, body mass index, cardiovascular disease, depression, diabetes, self-rated health, high cholesterol, hypertension, peripheral vascular disease, physical activity, smoking, and history of stroke. Associations with risk factors were determined for a global cognitive composite outcome (memory, language, processing speed, and executive functioning tests) and Mini-Mental State Examination score. Individual participant data meta-analyses of multivariable linear mixed model results pooled across cohorts revealed that for at least 1 cognitive outcome, age (B = â0.1, SE = 0.01), APOE*4 carriage (B = â0.31, SE = 0.11), depression (B = â0.11, SE = 0.06), diabetes (B = â0.23, SE = 0.10), current smoking (B = â0.20, SE = 0.08), and history of stroke (B = â0.22, SE = 0.09) were independently associated with poorer cognitive performance (p < 0.05 for all), and higher levels of education (B = 0.12, SE = 0.02) and vigorous physical activity (B = 0.17, SE = 0.06) were associated with better performance (p < 0.01 for both). Age (B = â0.07, SE = 0.01), APOE*4 carriage (B = â0.41, SE = 0.18), and diabetes (B = â0.18, SE = 0.10) were independently associated with faster cognitive decline (p < 0.05 for all). Different effects between Asian people and white people included stronger associations for Asian people between ever smoking and poorer cognition (group by risk factor interaction: B = â0.24, SE = 0.12), and between diabetes and cognitive decline (B = â0.66, SE = 0.27; p < 0.05 for both). Limitations of our study include a loss or distortion of risk factor data with harmonization, and not investigating factors at midlife. Conclusions: These results suggest that education, smoking, physical activity, diabetes, and stroke are all modifiable factors associated with cognitive decline. If these factors are determined to be causal, controlling them could minimize worldwide levels of cognitive decline. However, any global prevention strategy may need to consider ethno-regional differences
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